Suggest topics based on search phrases (behind experimental). (#8186)

Author: isoos

app/lib/frontend/handlers/experimental.dart

@@ -8,8 +8,9 @@ import '../../shared/cookie_utils.dart';
 
 const _publicFlags = <String>{
   'dark',
-  'search-completion',
   'download-counts',
+  'search-completion',
+  'search-topics',
 };
 
 const _allFlags = <String>{
@@ -86,6 +87,7 @@ class ExperimentalFlags {
   }
 
   bool get isSearchCompletionEnabled => isEnabled('search-completion');
+  bool get isSearchTopicsEnabled => isEnabled('search-topics');
 
   bool get isDarkModeEnabled => isEnabled('dark');
   bool get isDarkModeDefault => isEnabled('dark-as-default');

app/lib/frontend/templates/listing.dart

@@ -6,6 +6,7 @@ import 'dart:math';
 
 import 'package:_pub_shared/search/search_form.dart';
 import 'package:collection/collection.dart';
+import 'package:pub_dev/frontend/request_context.dart';
 
 import '../../package/search_adapter.dart';
 import '../../search/search_service.dart';
@@ -51,6 +52,9 @@ String renderPkgIndexPage(
       messageFromBackend: searchResultPage.errorMessage,
     ),
     nameMatches: _nameMatches(searchForm, searchResultPage.nameMatches),
+    topicMatches: requestContext.experimentalFlags.isSearchTopicsEnabled
+        ? _topicMatches(searchForm, searchResultPage.topicMatches)
+        : null,
     packageList: packageList(searchResultPage),
     pagination: searchResultPage.hasHit ? paginationNode(links) : null,
     openSections: openSections,
@@ -147,3 +151,24 @@ d.Node? _nameMatches(SearchForm form, List<String>? matches) {
     }),
   ]);
 }
+
+d.Node? _topicMatches(SearchForm form, List<String>? matches) {
+  if (matches == null || matches.isEmpty) {
+    return null;
+  }
+  final singular = matches.length == 1;
+  final isExactNameMatch = singular && form.parsedQuery.text == matches.single;
+  final nameMatchLabel = isExactNameMatch
+      ? 'Exact topic match: '
+      : 'Matching ${singular ? 'topic' : 'topics'}: ';
+
+  return d.p(children: [
+    d.text(nameMatchLabel),
+    ...matches.expandIndexed((i, name) {
+      return [
+        if (i > 0) d.text(', '),
+        d.a(href: urls.searchUrl(q: 'topic:$name'), text: '#$name'),
+      ];
+    }),
+  ]);
+}

app/lib/frontend/templates/views/pkg/index.dart

@@ -14,14 +14,22 @@ d.Node packageListingNode({
   required SearchForm searchForm,
   required d.Node listingInfo,
   required d.Node? nameMatches,
+  required d.Node? topicMatches,
   required d.Node packageList,
   required d.Node? pagination,
   required Set<String>? openSections,
 }) {
+  final matchHighlights = [
+    if (nameMatches != null) nameMatches,
+    if (topicMatches != null) topicMatches,
+  ];
   final innerContent = d.fragment([
     listingInfo,
-    if (nameMatches != null)
-      d.div(classes: ['listing-highlight-block'], child: nameMatches),
+    if (matchHighlights.isNotEmpty)
+      d.div(
+        classes: ['listing-highlight-block'],
+        children: matchHighlights,
+      ),
     packageList,
     if (pagination != null) pagination,
     d.markdown('Check our help page for details on '

app/lib/package/search_adapter.dart

@@ -43,6 +43,7 @@ class SearchAdapter {
       form,
       result.totalCount,
       nameMatches: result.nameMatches,
+      topicMatches: result.topicMatches,
       sdkLibraryHits: result.sdkLibraryHits,
       packageHits:
           result.packageHits.map((h) => views[h.package]).nonNulls.toList(),
@@ -146,6 +147,9 @@ class SearchResultPage {
   /// would be considered as blocker for publishing).
   final List<String>? nameMatches;
 
+  /// Topic names that are exact name matches or are close to a known topic.
+  final List<String>? topicMatches;
+
   /// The hits from the SDK libraries.
   final List<SdkLibraryHit> sdkLibraryHits;
 
@@ -163,6 +167,7 @@ class SearchResultPage {
     this.form,
     this.totalCount, {
     this.nameMatches,
+    this.topicMatches,
     List<SdkLibraryHit>? sdkLibraryHits,
     List<PackageView>? packageHits,
     this.errorMessage,

app/lib/search/mem_index.dart

@@ -8,6 +8,7 @@ import 'package:_pub_shared/search/search_form.dart';
 import 'package:clock/clock.dart';
 import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
+import 'package:pub_dev/service/topics/models.dart';
 
 import '../shared/utils.dart' show boundedList;
 import 'models.dart';
@@ -37,6 +38,13 @@ class InMemoryPackageIndex {
   late final List<PackageHit> _likesOrderedHits;
   late final List<PackageHit> _pointsOrderedHits;
 
+  // Contains all of the topics the index had seen so far.
+  // TODO: consider moving this into a separate index
+  // TODO: get the list of topics from the bucket
+  final _topics = <String>{
+    ...canonicalTopics.aliasToCanonicalMap.values,
+  };
+
   late final DateTime _lastUpdated;
 
   InMemoryPackageIndex({
@@ -57,6 +65,12 @@ class InMemoryPackageIndex {
           }
         }
       }
+
+      // Note: we are not removing topics from this set, only adding them, no
+      //       need for tracking the current topic count.
+      _topics.addAll(doc.tags
+          .where((t) => t.startsWith('topic:'))
+          .map((t) => t.split('topic:').last));
     }
 
     final packageKeys = _documents.map((d) => d.package).toList();
@@ -170,7 +184,21 @@ class InMemoryPackageIndex {
     }
 
     final nameMatches = textResults?.nameMatches;
+    List<String>? topicMatches;
     List<PackageHit> packageHits;
+
+    if (parsedQueryText != null) {
+      final parts = parsedQueryText
+          .split(' ')
+          .map((t) => canonicalTopics.aliasToCanonicalMap[t] ?? t)
+          .toSet()
+          .where(_topics.contains)
+          .toList();
+      if (parts.isNotEmpty) {
+        topicMatches = parts;
+      }
+    }
+
     switch (query.effectiveOrder ?? SearchOrder.top) {
       case SearchOrder.top:
         if (textResults == null) {
@@ -229,6 +257,7 @@ class InMemoryPackageIndex {
       timestamp: clock.now().toUtc(),
       totalCount: totalCount,
       nameMatches: nameMatches,
+      topicMatches: topicMatches,
       packageHits: packageHits,
     );
   }

app/lib/search/search_service.dart

@@ -312,6 +312,9 @@ class PackageSearchResult {
   /// Package names that are exact name matches or close to (e.g. names that
   /// would be considered as blocker for publishing).
   final List<String>? nameMatches;
+
+  /// Topic names that are exact name matches or close to the queried text.
+  final List<String>? topicMatches;
   final List<SdkLibraryHit> sdkLibraryHits;
   final List<PackageHit> packageHits;
 
@@ -325,6 +328,7 @@ class PackageSearchResult {
     required this.timestamp,
     required this.totalCount,
     this.nameMatches,
+    this.topicMatches,
     List<SdkLibraryHit>? sdkLibraryHits,
     List<PackageHit>? packageHits,
     this.errorMessage,
@@ -339,6 +343,7 @@ class PackageSearchResult {
   })  : timestamp = clock.now().toUtc(),
         totalCount = 0,
         nameMatches = null,
+        topicMatches = null,
         sdkLibraryHits = <SdkLibraryHit>[],
         packageHits = <PackageHit>[];
 
@@ -358,6 +363,7 @@ class PackageSearchResult {
       timestamp: timestamp,
       totalCount: totalCount,
       nameMatches: nameMatches,
+      topicMatches: topicMatches,
       sdkLibraryHits: sdkLibraryHits ?? this.sdkLibraryHits,
       packageHits: packageHits,
       errorMessage: errorMessage,